P0107 MAP sensor circuit low - bouncing kPa
Thread Starter
Joined: Jan 2002
Posts: 4,069
Likes: 74
From: Casselberry FL
P0107 MAP sensor circuit low - bouncing kPa Over the last few days, randomly while driving, the car started bucking horrendously. It didn't want to accelerate and sometimes would outright stall while driving. It's as if Michael J Fox is remotely controlling my throttle. It would start up again, continue having seizures and after nursing it along for a relatively short period of time (say within a 1/4mi), the bucking would decide to go away. It would randomly come back again later during driving. Finally got a P0107. Putting a scanner on it, when the bucking occurs the MAP kPa is bouncing pretty severely +/- 30kPa, causing the load & fueling to bounce around (I'm speed density only at the moment) Even though I've read that when a MAP sensor fails it will read 101kPA, I had a new ACDelco MAP sensor that I threw in tonight. I've also ordered a replacement MAP extension harness in case something failed in it during maintenance. Per my Helms manual, I had trouble trying to measure +5V on the MAP harness connector, perhaps I was doing it wrong? They wanted me to short two pins on the harness and see the reported voltage in the scanner, but I don't have a MAP voltage PID in HPTuners. Tried it with a DMM but didn't see 5V with the ignition in the run position, engine off.
What changed recently: I had been running MAF only for many months (I'm wondering if running MAF only may have been masking a MAP problem?). Within the last few weeks I had begun getting some strange surging at idle, and idle hanging high coming to a stop when the engine wasn't warmed up. A few months earlier, the 3/8" fuel line I got from MightyMouse pulled my LS3 valley cover nipple out during maintenance, even trying to be gentle with rotating the hose. So the nipple had been pushed in but not sealed well for a period of time. I didn't want wory about an unreliable repair in the back of my mind, so I just bought a new valley cover which included the gasket.
Around July 6th, I changed from MAF only to SD onIy to see if the drivability was better (it was) and there was less surging at idle but still not as good as it had been in the past.
On July 8th, I swapped the valley cover. I torqued everything behind the TB to factory spec (valley cover bolts, injector rail bolts, intake manifold bolts). One of the intake manifold bolts would not tighten on the middle passenger side. I seem to recall I had a busted bolt in that location back in 2019, and the shop was supposed to fix it during the rebuild. Unsure of the current issue for that bolt not tightening, I think maybe it was like that the last time I took off the intake in 2020 also. While I was in there I looked inside the manifold to see how well the MMS can was working, and it was working very well, just a hint of brown mist wiped from the bottom of the intake since last year, tiny bit of oil residue at the bottom of the TB seal. The intake ports are about how I remembered them when I re-assembled it last year with all new TB & manifold gaskets, but still a bit brown. Didn't replace those seals this time. So I figured I'll run some X66P through the TB PCV hose (I poured the X66P into a new spray bottle and sprayed it in the hose) to see if I could clean some of the residue off the intake ports and potentially off the valves & chambers. Yeah, I know X66P is designed to be used through the spark plug hole, but well, I'm too lazy for that ordeal. Got some smoke out the exhaust while spraying it in (I didn't stall the engine) I think it took maybe 10 minutes to spray in. Waited 3 hours and drove it around, couldn't get much smoke out of it even at WOT, but it was 10-11PM also. I re-used the old MAP sensor, but I changed from using RTV to seal the sensor to using the Magnuson MAP sensor bracket. It uses a round metal cylinder that fits snuggly into the LS3 MAP hole, which allows the LS1 MAP sensor to be snug inside that metal cylinder, plus a metal clamp held on my a screw. Seems to be equally secure as the RTV solution. I installed the MighyMouse quick connects with HPS HTHH-038 hose, which will soon be replaced with HPS FKM-038 hose.
July 9th changed the oil and trying a WIX for the first time (57060) instead of the K&Ns I've used for two decades. I chose 57060 instead of XP because Wix's XP synthetic media filters worse than their non-XP media. Also replaced the ABS module due to a failed solenoid.
MAP bucking symptoms began the morning of July 12th, the first day I received the P0107. Short of replacing the MAP harness and the broken intake manifold bolt, is there anything else I should be looking at?
What changed recently: I had been running MAF only for many months (I'm wondering if running MAF only may have been masking a MAP problem?). Within the last few weeks I had begun getting some strange surging at idle, and idle hanging high coming to a stop when the engine wasn't warmed up. A few months earlier, the 3/8" fuel line I got from MightyMouse pulled my LS3 valley cover nipple out during maintenance, even trying to be gentle with rotating the hose. So the nipple had been pushed in but not sealed well for a period of time. I didn't want wory about an unreliable repair in the back of my mind, so I just bought a new valley cover which included the gasket.
Around July 6th, I changed from MAF only to SD onIy to see if the drivability was better (it was) and there was less surging at idle but still not as good as it had been in the past.
On July 8th, I swapped the valley cover. I torqued everything behind the TB to factory spec (valley cover bolts, injector rail bolts, intake manifold bolts). One of the intake manifold bolts would not tighten on the middle passenger side. I seem to recall I had a busted bolt in that location back in 2019, and the shop was supposed to fix it during the rebuild. Unsure of the current issue for that bolt not tightening, I think maybe it was like that the last time I took off the intake in 2020 also. While I was in there I looked inside the manifold to see how well the MMS can was working, and it was working very well, just a hint of brown mist wiped from the bottom of the intake since last year, tiny bit of oil residue at the bottom of the TB seal. The intake ports are about how I remembered them when I re-assembled it last year with all new TB & manifold gaskets, but still a bit brown. Didn't replace those seals this time. So I figured I'll run some X66P through the TB PCV hose (I poured the X66P into a new spray bottle and sprayed it in the hose) to see if I could clean some of the residue off the intake ports and potentially off the valves & chambers. Yeah, I know X66P is designed to be used through the spark plug hole, but well, I'm too lazy for that ordeal. Got some smoke out the exhaust while spraying it in (I didn't stall the engine) I think it took maybe 10 minutes to spray in. Waited 3 hours and drove it around, couldn't get much smoke out of it even at WOT, but it was 10-11PM also. I re-used the old MAP sensor, but I changed from using RTV to seal the sensor to using the Magnuson MAP sensor bracket. It uses a round metal cylinder that fits snuggly into the LS3 MAP hole, which allows the LS1 MAP sensor to be snug inside that metal cylinder, plus a metal clamp held on my a screw. Seems to be equally secure as the RTV solution. I installed the MighyMouse quick connects with HPS HTHH-038 hose, which will soon be replaced with HPS FKM-038 hose.
July 9th changed the oil and trying a WIX for the first time (57060) instead of the K&Ns I've used for two decades. I chose 57060 instead of XP because Wix's XP synthetic media filters worse than their non-XP media. Also replaced the ABS module due to a failed solenoid.
MAP bucking symptoms began the morning of July 12th, the first day I received the P0107. Short of replacing the MAP harness and the broken intake manifold bolt, is there anything else I should be looking at?
Thread Starter
Joined: Jan 2002
Posts: 4,069
Likes: 74
From: Casselberry FL
I installed the new MAP sensor on Wednesday the 14th. I didn't have the problem in limited driving Thu the 15th. I also checked the intake manifold bolt torque on Thursday evening and found a few to be just slightly loose and I retorqued them. I also loosened and torqued the TB bolts to spec. Started the car and it wouldn't turn over. Scanned it and noticed the IAT was -38... IAT sensor not fully snapped in after tightening TB bolts. Then it started but idled high for a few minutes before I shut it off. Scanning later showed TPS was 1.x% at idle with foot off pedal, cable routed correctly and performed a TPS reset. No significant issues the remainder of Friday while warm. Replaced front parking lamp bulbs, going to need a new 3157 lamp harness soon. Haven't started the car yet since yesterday aftenoon.
Today I'm trying to finally replace the vacuum line that goes between the vacuum block near the PCM to the tank near the passenger side horn. The block connection for this hose was capped, but the cap was cracked along the side. I ran the jerry-rigged hose repair to the vacuum block and capped it at the other end until I can get under the car. Received new IAC valve today (not installed, waiting to see if it's needed) and still waiting on MAP extension harness (if needed). Would a smoke test be adequate to determine of that broken intake manifold is causing a vacuum leak? Is there a better method? I'm not particularly concerned about the loose bolt unless it causes a detectable problem.
If it happens to only be a failed MAP sensor, then I wonder if it was coincidence or if it was related to the X66P cleaner spray could have gotten into the sensor through the intake and caused a side effect. Also wondering on the discrepancy of 'you know the MAP sensor is bad if it always reads 100kPA' that I found on the HPTuners forum.
Today I'm trying to finally replace the vacuum line that goes between the vacuum block near the PCM to the tank near the passenger side horn. The block connection for this hose was capped, but the cap was cracked along the side. I ran the jerry-rigged hose repair to the vacuum block and capped it at the other end until I can get under the car. Received new IAC valve today (not installed, waiting to see if it's needed) and still waiting on MAP extension harness (if needed). Would a smoke test be adequate to determine of that broken intake manifold is causing a vacuum leak? Is there a better method? I'm not particularly concerned about the loose bolt unless it causes a detectable problem.
If it happens to only be a failed MAP sensor, then I wonder if it was coincidence or if it was related to the X66P cleaner spray could have gotten into the sensor through the intake and caused a side effect. Also wondering on the discrepancy of 'you know the MAP sensor is bad if it always reads 100kPA' that I found on the HPTuners forum.
